Wireless communication system, wireless communication control apparatus and wireless communication control method, and computer program

ABSTRACT

A communication terminal under the control of a wireless base station recursively has wireless base station capabilities in a parent network, constructs a daughter network within a scope of resources of the own apparatus assigned by the wireless base station, and assigns the resources to an other communication terminal under the control of the communication terminal having base station capabilities. This novel constitution allows to configure two or more networks guaranteed not to interfere each other, thereby allowing the coexistence of a plurality of personal area networks on a same frequency channel. At the same time, the novel constitution allows expanding a network area without increasing the scale of equipment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/332,304, filed on May 5, 2003, now U.S. Pat. No. 7,729,293, which isa national stage application under 35 U.S.C. §371 of InternationalApplication No. PCT/JP02/04376, filed May 1, 2002, which claims priorityfrom Japanese Application Nos. 2001-177783, filed May 8, 2001,2001-253701, filed Aug. 23, 2001, and 2002-115063, filed Apr. 17, 2002,the disclosures of which are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to a wireless communicationsystem, a wireless communication control apparatus and a wirelesscommunication control method, and a computer program which realizemutual communication between a plurality of wireless stations and, moreparticularly, to a wireless communication system, a wirelesscommunication control apparatus and a wireless communication controlmethod, and a computer program which realize the construction of anetwork under the control of a particular control station.

To be more specific, the present invention relates generally to awireless communication system in which a plurality of wireless networksexist at the same time, a wireless communication control apparatus and awireless communication control method for controlling the communicationoperation in each of a plurality of contending wireless networks, and acomputer program. Still more specific, the present invention relates toa wireless communication system in which a plurality of wirelessnetworks contending with each other at a same frequency band exist atthe same time, a wireless communication control apparatus and a wirelesscommunication control method for controlling the communication operationin each of a plurality of wireless networks contending with each otherat a same frequency band, and a computer program. (It should be notedthat the “same frequency band” referred to herein includes UWB (UltraWide Band) wireless communications technology by which data aretransferred as spread over ultra wide band.)

2. Background Art

Configuring a LAN (Local Area Network) by interconnecting a plurality ofcomputers allows the sharing of information such as files and data, thesharing of peripheral devices such as printers, and the exchanging ofinformation such as electronic mail and content data.

Conventionally, it is a general practice to perform LAN connections in awired manner based on optical fibers, coaxial cables, or twisted-paircables. This requires line laying work, making it difficult to constructnetworks with ease and making cable wiring complicated. After theconstruction of a LAN, the moving range of apparatuses is limited by thecable lengths, thereby making it inconvenient to use the constructedsystem. To free the users from the conventional wired LAN systems,wireless LANs have been attracting attention of those who are concerned.According to wireless LANs, most of the cables laid in offices and otherwork spaces can be left out, thereby making it comparatively easy tomove communication terminals personal computers (PCs).

Recently, because of their enhanced transmission speeds and reducedcosts, wireless LAN systems have been increasingly in high demand.Especially, it is a recent trend that the communication of informationis performed by constructing small-scale wireless networks among pluralpersonal electronic devices, so that researches are being made into theintroduction of a personal area network (PAN). For example, PANspecifies different wireless combination systems based on 2.4 GHz and 5GHz bands, which do not require the license from authorities concerned.

For example, the IEEE 802.15.3 standardizes personal area networkshaving transfer rates higher than 20 Mbps. This IEEE section is mainlypromoting the standardization based on the PHY layer mainly usingsignals of 2.4 GHz band.

In these wireless personal networks, one wireless communicationapparatus operates as a control station called a “coordinator” aroundwhich a personal area network is constructed within a range of about 10meters. The coordinator transmits a beacon signal at a predeterminedperiod and this beacon period is specified as a transmission frameperiod. At every transmission frame period, the time slots to be used bythe wireless communication apparatuses of the wireless personal networkare assigned.

For the time slot assigning, methods called “guaranteed time slot (GTS)”and “dynamic TDMA (Time Division Multiple Access)” for example are usedin which a communication method is assumed for dynamically assigningtransmission time slots while guaranteeing a predetermined transmissioncapacity.

For example, the MAC layer standardized by the IEEE 802.15.3 preparesthe contention access period (CAP) and the contention free period (CFP).For asynchronous communication, the contention access period is used toexchange short data and command information. For stream communication,dynamic time slot assignment is performed by the guaranteed time slot(GTS) in the contention free period, thereby performing guaranteed timeslot transmission.

The MAC layer portion standardized by the IEEE 802.15.3 is specified sothat it is applicable as the standard specifications of the PHY layer inaddition to the PHY layer based on 2.4 GHz band signal. Also, thestandardizing activities have begun for the application of the PHY layerstandardized by the IEEE 802.1.5.3 to other PHY layers than the PHYlayer based on 2.4 GHz band signal.

Recently, wireless LAN (Local Area Network) systems based on SS (SpreadSpectrum) technologies have been put into practical use. Also recentlyproposed is the UWB (Ultra Wide Band) transmission scheme based on theSS intended for applications such as PAN.

The DS (Direct Spread) scheme, which is one of SS schemes, multiplies aninformation signal by a random code sequence called PN (Pseudo Noise) tospread the occupied band and transmits the resultant signal on thetransmitting side; on the receiving side, the received spreadinformation signal is multiplied by the PN code for de-spread toreproduce the information signal. In the UWB scheme, this informationsignal spread rate is maximized by which a high-speed data transmissionis realized by performing to transmit/receive data such that the data isspread over an ultra high frequency band of 2 GHz to 6 GHz for example.

In the UWB scheme, an information signal is configured by use of impulsesignal trains each having a period of as short as several 100picoseconds and this signal train is transferred. Its occupied bandwidth is in GHz order so that the value obtained by dividing theoccupied band width by its center frequency (for example, 1 GHz to 10GHz) becomes about 1, which is a ultra wide band as compared with theband widths commonly used in wireless LANs based on so-called W-CDMA,cdma 2000, SS (Spread Spectrum), and OFDM (Orthogonal Frequency DivisionMultiplexing) schemes.

Referring to FIG. 20, there is shown an example of the data transmissionbased on the UWB scheme. Input information 901 is spread by a spreadsequence 902. In some systems based on UWB, the multiplication of thisspread sequence is left out.

An information signal 903 resulted from the spectrum spread isdemodulated by use of the impulse signal (wavelet pulse) of the UWBscheme (905). This modulation is based on PPM (Pulse PositionModulation), biphase modulation, or amplitude modulation for example.

The impulse signal used on the UWB scheme is an extremely thin pulse, sothat the UWB scheme uses extremely wide band in terms of frequencyspectrum. Consequently, the inputted information signal has only a powerthat is lower than the noise level in each frequency area.

A received signal 905 is mixed with noise, but it can be detected bycomputing the correlation value between the receive signal and theimpulse signal. In addition, because signal spread is performed in manysystems, many impulse signals are transmitted for one bit of transmitinformation. Hence, a receive correlation value 907 of each impulsesignal may be integrated by the length of spread sequence (908), therebyfurther facilitating the detection of the transmit signal.

The signal spread by the UWB transmission scheme has only a power lowerthan the noise level in each frequency area, so that it is comparativelyeasy for each communication system based on the UWB transmission schemeto coexist with communication systems based on other communicationschemes.

When a communication environment is considered in which, with the recentpopularization of information devices such as personal computers (PCs)and installation of many various devices in offices, these devices areinterconnected by two or more wireless networks packed in a narrow workenvironment, thus causing plural wireless networks coexist in samefrequency band. The “same frequency band” herein includes the UWBwireless communication scheme, which transfers data by spreading themover a very wide frequency band.

The PHY layer specifications using the 2.4 GHz band signal standardizedby the above-mentioned IEEE 802.15.3 must consider the coexistence withother plural wireless communication systems existing in the samefrequency band.

Especially, in the case of the UWB wireless communication network, dataare transferred by spreading them over an extremely wide band, so thatit is highly possible for this network to contend with adjacent wirelesscommunication networks.

On the other hand, an impulse signal train used in the UWB wirelesscommunication scheme has no particular frequency carrier, so that it isdifficult to perform a carrier sense operation. Therefore, if the UWBwireless communication scheme is applied as the PHY layer of the IEEE802.15.3, the carrier sense standardized by this section cannot be usedfor access control because there is no particularly carrier signal,thereby having to resort to the access control based on time divisionmultiplexing.

If a small-scale wireless network system such as PAN is put intoconsideration, each network (or base station) is not always fixed, sothat, if a new network is constructed in the same space or a network ismoved to the same space from another space for example, the problems ofthe contention between networks and the dynamic assignment of time slots(or resources) must be solved.

For example, Japanese Patent Laid-open No. 2000-299670 assigned to theapplicant hereof discloses a network system, by assigning at least oneof plural divided slots to a control slot, which transmits theinformation suitable for the network status and the contents ofinformation to be transmitted.

The above-mentioned disclosed network system is based on a method inwhich each terminal station reports interfered slots to the controlstation and the control station circumvents these interfered slots touse the network.

However, this method in which each terminal station reports to thecontrol station requires a means for reporting to the control stationfrom time to time, thereby presenting a problem of increasing thefrequency of reporting if there are plural adjacent networks.

In addition, the above-mentioned method, because the usage status ofeach slot is known by detecting a predetermined synchronous signal, allframe structures used by other networks cannot be understood.

Japanese Patent Publication No. 2,660,189 discloses a method andapparatus capable of dynamically assign a bandwidth to plural cellswithin a cellular network. However, according to this application, thedisclosed method and apparatus must organize plural cell groups called“super cells” such that the interference between cells is minimized. Therequest for channel band widths is performed in accordance with the userrequest in each cell, namely, the request from the mobile stations (MS)belonging to each base station (BS). In other words, if plural networkscoexist in the same space, the request for channel bandwidths has norelationship with how to solve the problem of contention between thebase stations. Further, the above-mentioned Japanese patent publicationdoes not solve the problems of the contention between networks anddynamic assignment of time slots (or resources) in the case where a newnetwork is constructed in the same space or a network moves to this samespace from another space.

Japanese Translations of PCT for Patent No. 2001-518766 (WO99/17575)discloses a method in which, by dynamically dividing the datatransmitting resources by plural networks, each network divides theassigned resources among its users in accordance with its own channelassigning method. This application is based on the concept in which theoperators mutually accommodate the plural frequency channels existing inthe same space to operate the network, thereby realizing the dynamicassignment of frequency channels by borrowing the (frequency) bands ofdifferent operators in a cellular network.

However, the above-mentioned application treats the problem of dynamicassignment of the transmitting resources between the base stations whichare arranged in a fixed manner, so that it is presumed that a minimumtime slot be prepared for each network (or base station) from the verystart. Further, each network (or base station) arranged in a fixedmanner requires the minimum resource assignment for accommodating theusers, so that there is no state in which no resource is assigned to thenetwork. In other words, the above-mentioned application does notpropose any scheme, procedure, and method for a network newlyconstructed in the same space or moving thereto from another space toget resources from the state in which no resource is assigned to thenetwork. The above-mentioned application does not refer to any scheme,procedure, and method for a network already constructed in a space toassign resources to a network that newly appears in the same space.

BRIEF SUMMARY OF THE INVENTION

It is therefore a main object of the present invention to provide anexcellent wireless communication system which allows the coexistence ofa plurality of mutually contending wireless networks and an excellentwireless communication control apparatus and method and an excellentcomputer program which preferably control the communications operationin each communication network in a communication environment in which aplurality of wireless networks contend with each other.

It is another object of the present invention to provide an excellentwireless communication system which allows the coexistence of aplurality of wireless networks contending with each other in a samefrequency band, an excellent wireless communication control apparatusand wireless communication control method, and an a computer programwhich preferably control the communications operation in eachcommunication network in a communication environment in which aplurality of wireless networks contend with each other in a samefrequency band.

It is still another object of the present invention to provide anexcellent wireless communication system, an excellent wirelesscommunication control apparatus and wireless communication controlmethod, and an excellent computer program which, if a plurality ofpersonal area networks exist on a same frequency channel, allow thecoexistence of these personal area networks by time-divisionmultiplexing transmission frame periods only by performing controlbetween transmission apparatuses which provide control stations.

It is yet another object of the present invention to provide anexcellent wireless communication system, an excellent wirelesscommunication control apparatus and wireless communication controlmethod, and an excellent computer program which solve the problems ofthe contention between networks in the case in which a new network isconstructed in a same space or a network moves to the same space fromanother space, thereby preferably performing dynamic assignment of timeslots (or resources).

In carrying out the invention and according to a first aspect thereof,there is provided a wireless communication control apparatus including:a communication control means for performing communication control inaccordance with a resource assignment included in a downstream signal ofa first network; and a resource assignment means for performing resourceassignment in accordance with a transmission request included in anupstream signal of a second network.

In the above-mentioned wireless communication apparatus, it ispreferable for the resource assigning means to perform resourceassignment to a communication apparatus, which gets under the control ofan own apparatus within a scope of resources assigned to the ownapparatus.

In carrying out the invention and according to a second aspect thereof,there is provided a wireless communication control method including thesteps of: receiving, in a downstream signal, by a first communicationterminal, resource assignment information determined by a wireless basestation apparatus in accordance with a transmission request from thefirst communication terminal apparatus; performing communication controlin the first communication terminal apparatus in accordance with theresource assignment information; and, performing resource assignment tothe second communication terminal apparatus within a scope of resourcesassigned to the first communication terminal apparatus from the wirelessbase station apparatus in the first communication terminal apparatus inresponse to a transmission request from a second communication terminalapparatus under the control of the first communication terminalapparatus.

In the above-mentioned wireless communication control method, it ispreferable for the second communication terminal apparatus torecursively perform, in response to the transmission request from another communication terminal apparatus which gets under the control ofthe own apparatus, resource assignment to the above-mentioned othercommunication terminal within a scope of resources assigned to the ownapparatus from the first communication terminal apparatus.

According to the wireless communication control apparatus of the firstaspect of the invention and the wireless communication control method ofthe second aspect of the invention, each communication terminal underthe control of the wireless base station in the parent networkrecursively has the wireless base station capabilities and performsresource assignment on each communication terminal under the control ofthe communication terminal having the wireless base station capabilitieswithin a scope of resources of the own apparatus assigned by thewireless base station. Consequently, the novel constitution mayconfigure two or more networks guaranteed not to interfere each other.

In carrying out the invention and according to a third aspect thereof,there is provided a wireless communication control method for performingresource assignment based on time division multiplexing, including thesteps of: assigning a first resource period within a transmission frameto a first station which constitutes a first network with a stationwhich assigns resource period at least to a own station; and assigning asecond resource period within the first resource period to a secondstation which constitutes a second network with at least the firststation.

In carrying out the invention and according to a fourth aspect thereof,there is provided a wireless communication system based on time divisionmultiplexing, including: a first station constituting a first networkwith a station which assigns a resource period to a own station tocommunicate with an other station constituting the first network; and asecond station constituting a second network with at least the firststation to communicate with an other station constituting the secondnetwork except for at least a portion of a resource period assigned tothe first station.

The term “system” herein used denotes a logical connection of aplurality of apparatuses (or a plurality of functional modules forrealizing a particular function) and it is not essential whether theseapparatuses or functional modules are accommodated in a single housing(this applies to the descriptions below).

In carrying out the invention and according to a fifth aspect thereof,there is provided a wireless communication system in which a wirelessnetworks constituted by a plurality of wireless communicationapparatuses and a control station for performing time slot assignment toeach of the plurality of wireless communication apparatuses in everypredetermined transmission frame period coexist, each of the wirelessnetworks including: a signal detecting means for detecting a signal froman other of the wireless networks; a time slot analyzing means foranalyzing a transmission time slot on which guaranteed time slottransmission is performed in an other of the wireless networks on thebasis of a signal detected by the signal detecting means; and a timeslot assigning means which does not assign a transmission time slot onwhich guaranteed time slot transmission is performed in an other of thewireless networks to a wireless communication apparatus in an ownwireless network.

The above-mentioned time slot assigning means may set the transmissiontime slot on which guaranteed time slot transmission is performed in another of the wireless networks as an unassigned area in the own wirelessnetwork. The above-mentioned time slot assigning means may clear thesetting of the unassigned area in the own wireless network in responseto that the signal detecting means does not detect the signal from another of the wireless networks.

The above-mentioned time slot analyzing means may analyze an unassignedarea in an other of the wireless networks and the above-mentioned timeslot assigning means may perform time slot assignment within the ownwireless network by use of the unassigned area in the other of thewireless networks.

Each wireless network is assigned with a time slot by a control station(or a coordinator) in every transmission frame period.

In carrying out the invention and according to a fifth aspect thereof,upon reception of beacon information from an other network, the controlstation of a receiving network decodes the received beacon informationand, on the basis of the time slot assignment information included inthe received beacon information, sets the time slot assigned area (orthe time area) as an unassigned area in the own network. Further, byexcluding the time slot assigned area (or the time area) used by another network, the control station of the own network can set again thetime slot assigned area (or the time area) for use in the own network.

Consequently, all wireless networks can coexist on a same frequencychannel by performing network operations as equals while avoidinginterference with each other. (It should be noted that the term “samefrequency band” used herein denotes the UWB wireless communicationscheme in which data are spread over an extremely wide frequency bandfor transmission and reception.)

In carrying out the invention and according to a sixth aspect thereof,there is provided a wireless communication control apparatus or methodfor performing, in a network environment in which a plurality ofwireless networks for performing guaranteed time slot transmission inevery predetermined transmission frame period between wirelesscommunication apparatuses coexist, time slot assignment of atransmission frame period within the wireless networks, including thesteps of: detecting a signal from an other of the wireless networks;analyzing a transmission time slot on which guaranteed time slottransmission is performed in an other of the wireless networks on thebasis of the signal detected in the signal detecting step; and notassigning a transmission time on which guaranteed time slot transmissionis performed on an other of the wireless networks to a wirelesscommunication apparatus in an own wireless network.

The above-mentioned time slot assigning step may set the transmissiontime slot on which guaranteed time slot transmission is performed on theother of the wireless networks as an unassigned area within the ownwireless network. The above-mentioned time slot assigning step may clearthe setting of the unassigned area in the own wireless network inresponse to that the signal detecting step does not detect the signalfrom the other of the wireless networks.

The above-mentioned time slot analyzing step may analyze an unassignedarea in the other of the wireless networks and the time slot assigningstep may perform time slot assignment within the own wireless network byuse of the unassigned area in the other of the wireless networks.

According to the wireless communication control apparatus and method ofthe sixth aspect of the invention, upon reception of beacon informationfrom an other network, the control station of a receiving networkdecodes the received beacon information and, on the basis of the timeslot assignment information included in the received beacon information,sets the time slot assigned area as an unassigned area in the ownnetwork. Further, by excluding the time slot assigned area used by othernetwork, the control station of the own network can set again the timeslot assigned area for use in the own network.

Consequently, all control stations constituting wireless networks cancoexist on a same frequency channel by performing network operations asequals while avoiding interference with each other.

In carrying out the invention and according to a seventh aspect thereof,there is provided a wireless communication system in which a pluralityof wireless networks constituted by a plurality of wirelesscommunication apparatuses and a control station for performing time slotassignment to each of the wireless communication apparatuses in everypredetermined transmission frame period coexist, at least one of thewireless networks providing: in response to the reception of a requestfor constructing a new wireless network, a transmission time slot forthe new wireless network.

In the wireless communication system according to the seventh aspect ofthe invention, a parent and daughter relationship as it were is formedbetween an existing wireless network and a wireless network to be newlyconstructed, in which the new wireless network operates as the daughterand the existing wireless network supports the construction of the newwireless network as the parent. Namely, in response to the reception bythe existing wireless network of a request for constructing a newwireless network, the existing wireless network provides a transmissiontime slot for the new wireless network, thereby avoiding theinterference between the wireless networks to realize the coexistence ona same frequency channel.

Consequently, according to the wireless communication system of theseventh aspect of the invention, if a network for which no time slot isassigned appears as with the case in which a new network is constructedin a same space or an other network moves thereto from an other spacefor example, the problem of the contention between the networks can besolved and the dynamic assignment of time slots (or resources) can beperformed in a preferable manner. Further, each already constructednetwork can dynamically assign its resources to any network newlyappearing in the same space.

Each of the wireless networks may include a setting means for setting atime slot unassigned area to an own wireless network; a transmittingmeans for transmitting time slot assignment information of the ownwireless network; an analyzing means for receiving and analyzing timeslot assignment information of an other wireless network; and aassigning means for assigning a time slot of the own wireless network byuse of an unassigned area of a time slot in an other wireless network.

The above-mentioned construction request may be a request forparticipating of an other control station that constructs a new wirelessnetwork into the corresponding wireless network or a request from another control station that constructs a new wireless network for a timeslot to a control station of the corresponding wireless network.

Further, information that a transmission time slot has been set to thenew wireless network may be included in time slot assignment informationsuch as a beacon signal and notified in the corresponding wirelessnetwork, or a transmission frame for notifying the new wireless networkof the setting of a transmission time slot may be directly transmitted.

In carrying out the invention and according to the eighth aspectthereof, there is provided a wireless communication control apparatus ormethod for performing, in a network environment in which a plurality ofwireless networks for performing guaranteed time slot transmission inevery predetermined transmission frame period between wirelesscommunication apparatuses coexist, time slot assignment in atransmission frame period in the wireless networks, wherein a requestfor constructing a new wireless network is transmitted to any of theexisting wireless networks.

In carrying out the invention and according to a ninth aspect thereof,there is provided a wireless communication control apparatus or methodfor performing, in a network environment in which a plurality ofwireless networks for performing guaranteed time slot transmission inevery predetermined transmission frame period between wirelesscommunication apparatuses coexist, time slot assignment in atransmission frame period in the wireless networks, wherein in responseto the reception of a request for constructing a new wireless network, atransmission time slot for the new wireless network is set.

The wireless communication control apparatus implementing the eighthaspect of the invention functions as the control station of the daughternetwork and the wireless communication control apparatus implementingthe ninth aspect of the invention functions as the control station ofthe parent network, so that the interference between the networks can beavoided, thereby realizing the coexistence on a same frequency channel.

For example, if the daughter network has been newly constructed in asame space of the parent network or the daughter network has moved to asame space of the parent network, no time slot is initially assigned tothe daughter network at all, but the contention between the networks canbe solved and a time slot (or resources) can be assigned to the daughternetwork in a preferable manner in the novel constitution.

The above-mentioned construction request may be a request forparticipating of an other control station that constructs a new wirelessnetwork into the corresponding wireless network or a request from another control station that constructs a new wireless network for a timeslot to a control station of the corresponding wireless network.

Further, information that a transmission time slot has been set to thenew wireless network may be included in time slot assignment informationsuch as a beacon signal and notified in the corresponding wirelessnetwork, or a transmission frame for notifying the new wireless networkof the setting of a transmission time slot may be directly transmitted.

In carrying out the invention and according to a tenth aspect thereof,there is provided a computer-readable program for executing, on acomputer system, processing of performing, in a network environment inwhich a plurality of wireless networks for performing guaranteed timeslot transmission in every predetermined transmission frame periodbetween wireless communication apparatuses coexist, time slot assignmentin a transmission frame period in the wireless networks, including thesteps of: detecting a signal from an other of the wireless networks;analyzing a transmission time slot on which guaranteed time slottransmission is performed in an other of the wireless networks on thebasis of the signal detected in the signal detecting step; and notassigning a transmission time slot on which guaranteed time slottransmission is performed on an other of the wireless networks to awireless communication apparatus in an own wireless network.

In carrying out the invention and according to an eleventh aspectthereof, there is provided a computer-readable program for executing, ona computer system, processing of performing, in a network environment inwhich a plurality of wireless networks for performing guaranteed timeslot transmission in every predetermined transmission frame periodbetween wireless communication apparatuses coexist, time slot assignmentin a transmission frame period in the wireless networks, including thesteps of: receiving a request for constructing a new wireless network;performing time slot assignment with a time slot unassigned area set inan own wireless network in response to the construction request; andtransmitting time slot assignment information in the own wirelessnetwork.

In carrying out the invention and according to a twelfth aspect ofthereof, there is provided a computer-readable program for executing, ona computer system, processing of performing, in a network environment inwhich a plurality of wireless networks for performing guaranteed timeslot transmission in every predetermined transmission frame periodbetween wireless communication apparatuses coexist, time slot assignmentin a transmission frame period in the wireless networks, including thesteps of: transmitting a request for constructing a new wireless networkto any of the existing wireless networks; receiving time slot assignmentinformation from any of the existing wireless networks; and performingtime slot assignment in an own wireless network on the basis of the timeslot assignment information.

The computer programs of the tenth through the twelfth aspects of theinvention define computer-readable programs, which realize predeterminedprocessing on a computer system. In other words, installing the computerprogram of the tenth aspect of the invention on a computer systemrealizes a cooperative operation on the computer system to obtain thesame effects as those provided by the wireless communication system ofthe fifth aspect of the invention. Installing the computer programs ofthe eleventh and twelfth aspects of the invention on a computer systemrealizes a cooperative operation on the computer system to obtain thesame effects as those of the seventh aspect of the invention.

These and other objects of the invention will be seen by reference tothe description, taken in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematic diagram conceptually illustrating a configuration of awireless communication system practiced as a first embodiment of theinvention.

FIG. 2 is a block diagram illustrating a configuration of acommunication terminal apparatus, which operates as a wireless basestation for performing wireless communication with other communicationterminal apparatuses within a wireless network associated with the firstembodiment of the invention.

FIG. 3 is a block diagram illustrating a configuration of acommunication terminal apparatus, which operates as a user station forperforming wireless communication under the control of a base station.

FIG. 4 is a diagram illustrating an exemplary configuration of a TDMAframe for use in the wireless network associated with the firstembodiment of the invention.

FIG. 5 is a diagram illustrating how two personal area networks exist asspaced from each other.

FIG. 6 is a diagram illustrating how a first piconet 1 and a secondpiconet 2 exist as spatially overlapped.

FIG. 7 is a diagram illustrating a configuration of a transmission framefor use in a piconet associated with a second embodiment of theembodiment.

FIG. 8 is a block diagram illustrating a configuration of a wirelesscommunication apparatus 10, which operates in the piconet associatedwith the second embodiment of the invention.

FIG. 9 is a diagram illustrating an example of an operation sequencebetween a control station 11 of the first piconet 1 and a controlstation 21 of the second piconet.

FIG. 10 is a diagram illustrating a configuration of a transmissionframe for use in a process of setting an unassigned area in each of thefirst piconet 1 and the second piconet 2.

FIG. 11 is a diagram illustrating a configuration of a transmissionframe for use in a process of setting an unassigned area in each of thefirst piconet 1 and the second piconet 2.

FIG. 12 is a diagram illustrating a configuration of a transmissionframe for use in a process of setting an unassigned area in each of thefirst piconet 1 and the second piconet 2.

FIG. 13 is a diagram illustrating a configuration of a transmissionframe for use in a process of setting an unassigned area in each of thefirst piconet 1 and the second piconet 2.

FIG. 14 is a flowchart describing a processing operation of a controlstation for constructing piconets in order to realize the operationsequence shown in FIG. 9.

FIG. 15 is a diagram illustrating an operation sequence for realizingthe coexistence of the two piconets using a same frequency channel byavoiding the interference by each other while forming a parent anddaughter relationship.

FIG. 16 is a flowchart describing a processing procedure of a controlstation for realizing the coexistence with another piconet by avoidingthe interference by each other while forming a parent and daughterrelationship.

FIG. 17 is a diagram illustrating another example of an operationsequence for realizing the coexistence of two piconets having a samefrequency channel by avoiding the interference by each other whileforming a parent and daughter relationship.

FIG. 18 is a flowchart describing a processing procedure of the controlstation of the parent piconet for realizing the coexistence of thepiconets by avoiding the interference by each other in accordance withthe processing procedure between the piconets shown in FIG. 17.

FIG. 19 is a flowchart describing a processing procedure of the controlstation of the daughter piconet for realizing the coexistence of thepiconets by avoiding the interference by each other in accordance withthe operation procedure between the piconets shown in FIG. 17.

FIG. 20 is a diagram illustrating an example of data transmission basedon the UWB scheme.

DETAILED DESCRIPTION Best Mode for Carrying out the Invention

This invention will be described in further detail by way of examplewith reference to the accompanying drawings.

A. The First Embodiment

Now, referring to FIG. 1, there is shown a conceptual configuration of awireless communication system practiced as a first embodiment of theinvention.

As shown in FIG. 1, a wirelessly base station (hereafter abbreviated asa BS) wireless communicates with three mobile stations (hereafterabbreviated as MSs), which provide user stations of this wireless basestation, namely MS-A (user A), MS-B (user B), and MS-C (user C). BS,MS-A, MS-B, and MS-C constitute the parent network. One mobile stationMS-A has the capabilities of a wireless base station and wirelesslycommunicates with two mobile stations MS-D and MS-E, which are the userstations of the MS-A. The mobile station MS-A operating as a basestation and the mobile stations MS-D and MS-E constitute the daughternetwork.

Although not shown, the other mobile stations MS-B and MS-C may alsohave the base station capabilities. Namely, these mobile stations mayconstitute a daughter network by using other MSs as slaves. Obviously,the MS-D or MS-E in the daughter network configured with the MS-A usedas a slave may constitute a grandchild network by using other MSs asslaves.

Referring to FIG. 2, there is schematically shown a configuration of acommunication terminal apparatus, which operates as a wireless basestation for wirelessly communicating with other communication terminalapparatuses within a wireless network associated with the presentinvention.

An upstream signal transmitted from an MS is received by a radioreceiving section 112 via an antenna 111. The radio receiving section112 performs predetermined radio receiving processing (for example,down-conversion and A/D conversion) on the received upstream signal andoutputs the processed upstream signal to a demodulating section 113.

The demodulating section 113 demodulates this processed signal to outputreceiving data. The demodulating section 113 also demodulates a randomaccess channel (RACH) signal received from an MS to output atransmitting request signal to a request confirming section 114. Therequest confirming section 114 confirms a transmitting request by theRACH signal from each MS to output, to a scheduler 115, informationabout which MS has issued the transmitting request.

The scheduler 115 performs resource assignment of the MS from which thetransmitting request has been issued and outputs the resource assignmentinformation to a beacon inserting section 116. The beacon insertingsection 116 inserts the resource assignment information obtained in thescheduler 115 into the transmitting data and outputs the transmittingdata to a modulating section 117 as a transmitting signal.

The modulating section 117 modulates the transmitting signal and outputsthe modulated send signal to a radio transmitting section 118. The radiotransmitting section 118 performs predetermined radio transmittingprocessing (for example, D/A conversion and up-conversion) on themodulated signal and transmits the resultant signal to the MS via theantenna 111 as a downstream signal.

Referring to FIG. 3, there is schematically shown a configuration of acommunication terminal apparatus, which operates as a user station forperforming wireless communication under the control of a base station inthe wireless communication network associated with the invention.

A downstream signal transmitted from a BS or an MS functioning as a BSis received by a radio receiving section 122 via an antenna 121. Theradio receiving section 122 performs predetermined radio receivingprocessing (for example, down-conversion and A/D conversion) on thereceived signal and outputs the resultant signal to a demodulatingsection 123.

The demodulating section 123 demodulates the processed signal to outputreceiving data. The demodulating section 123 also demodulates a randomaccess channel (RACH) signal received from the MS (MS-D or MS-E) of thedaughter network, which becomes the slave of own apparatus and outputsthe demodulated signal to a request confirming section 125 as atransmitting request signal. Further, the demodulating section 123demodulates a beacon signal contained in the downstream signal from theBS and outputs the demodulated beacon signal to a beacon capturingsection 124.

The beacon capturing signal 124 reads the beacon resource assignmentinformation contained in the downstream signal transmitted from the BSor an MS functioning as the BS to recognize how the resource isassigned. This resource assignment information is outputted to acommunication control section 127. On the basis of the resourceassignment information, the communication control section 127 controls aframe configuring section 29 so as to perform time division multipleaccess (TDMA) communication. The frame configuring section 129frame-configures the transmitting data for the parent network andoutputs the configured data to a modulating section 130. Also, whenperforming a transmitting request operation on the BS or a MSfunctioning as the BS, the frame configuring section 129 inserts atransmitting request signal into the transmitting data for the parentnetwork.

The request confirming signal 125 confirms the transmitting request bythe RACH signal from each MS and outputs, to a scheduler 126, theinformation about which MS has transmitted the transmitting request. Thescheduler 126 performs resource assignment for the MS from which thetransmitting request has come and outputs the information about thisresource assignment to a beacon inserting section 128. The beaconinserting section 128 inserts the beacon signal, which is theidentification signal including the resource assignment informationobtained by the scheduler 126, into the transmitting data for thedaughter network and outputs the resultant data to the modulatingsection 130.

The modulating section 130 modulates the transmitting signal for theparent network and the transmitting signal for the daughter network andoutputs the modulated signals to radio transmitting section 131. Theradio transmitting section 131 performs predetermined radio transmittingprocessing (for example, D/A conversion and up-conversion) on themodulated signals and transmits the processed signals to the BS or theMS functioning as the BS via an antenna 121 as an upstream signal.

Referring to FIG. 4, there is shown a configuration of a TDMA frame foruse in the wireless network associated with the present embodiment. Thefollowing describes in detail a wireless communication method accordingto the present embodiment with reference to this figure. It should benoted that the communication terminal apparatus shown in FIG. 3 is MS-A.

First, as shown in the upper portion of FIG. 4, the BS shown in FIG. 1assigns resources to user A, user B, and user C. Namely, the beacon isfollowed by user A, user B, and user C, in this order. This resourceassignment information is contained in the beacon of the parent network.

The beacon of the parent network is sent from the BS to each MS. InMS-A, the beacon is read by the beacon capturing section 124 torecognize that the resource assignment to the MS-A is made immediatelyafter the beacon. The information about this resource assignment is sentto the communication control section 127. The communication controlsection 127 performs control so that the communication with the BS ismade during a period in which the resource is assigned.

The MS-A accepts resource requests (transmitting requests) from the MS-Dand the MS-E, which become the slaves of the MS-A. These transmittingrequests are made by the RACH in the contention partition of thedaughter network.

Then, the MS-A confirms the transmitting requests from the MS-D and theMS-E through the request confirming section 125 and sends the confirmedtransmitting requests to the scheduler 126. The scheduler 126 performsresource assignment on the MSs (in this example, MS-D and MS-E) fromwhich the transmitting requests have come. In this case, the MS-Aassigns the resources to the user stations of MS-D and MS-E, which arethe slaves of MS-A, within the scope of the resources assigned to theMS-A by the BS.

The information about the resource assignment determined by the MS-A issent to the MS-D and the MS-E by the beacon in the downstream signal ofthe daughter network. Thus, as shown in the lower portion of FIG. 4, theresource assignment is performed on the user D and the user E. Namely,the resource assignment is performed on the user D and the user E inthis order after the beacon.

Consequently, because the resource assignment is performed on the slavecommunication terminals within the scope of the resources assigned tothe master apparatus, the interference and disturbance between networkscan be avoided and prevented if they are configured in a same oradjacent area.

In the communication based on the above-mentioned TDMA frame, the MS(MS-A, MS-B, or MS-C) of the parent network requests the resourceassignment (the transmitting request) in the next frame by the RACH inthe contention partition and the BS performs the resource assignment ofthe next frame in response to the request and notifies the requesting MS(MS-A, MS-B, or MS-C) of the resource assignment in the next beacon.Then, the MS (MS-A, MS-B, or MS-C) performs communication based on theresource assignment information carried by the beacon.

The MS (MS-D or MS-E) of the daughter network requests the resourceassignment (the transmitting request) in the next frame by the RACH inthe contention partition and the MS-A performs the resource assignmentof the next frame in response to this request, notifying the MS (MS-D orMS-E) of the resource assignment by the next beacon. Then, the MS (MS-Dor MS-E) performs communication based on the resource assignmentinformation carried by the beacon.

Thus, in the present embodiment, each communication terminal, which isthe slave of the wireless base station in the parent network,recursively has the wireless base station capabilities and constructs adaughter network within a scope of the own apparatus's resourcesassigned by the wireless base station, thereby performing resourceassignment on its slave communication terminals. This novel constitutionallows configuring two or more networks, which are guaranteed not beinterfered each other. In addition, according to the present invention,the area of networks may be expanded without involving the increase inequipment scale.

Meanwhile, for new wireless technologies, which can effectively usefrequency resources, the ultra wide band (UWB) transmission scheme hasrecently been drawing attention. Basically, the ultra wide bandtransmission scheme performs base band transmission by use of a signalbased on pulse trains, each pulse having a very short pulse width (forexample, less than 1 ns (nanosecond). Its occupied bandwidth is on theGHz order so that the value obtained by dividing the occupied frequencybandwidth by its center frequency (for example, 1 GHz to 10 GHz) becomesabout 1. Therefore, the bandwidth of this scheme is ultra wide ascompared with those bandwidths used in wireless LANs based on theso-called W-CDMA scheme, cdma 2000 scheme, and SS (Spread Spectrum) andOFDM (Orthogonal Frequency Division Multiplexing).

In addition, the ultra wide band transmission scheme is characterized bythat, due to its lower signal power density characteristic, existingwireless systems having a high signal power density characteristic to aparticular frequency band are hardly interfered. Therefore, this schemeis expected as a technology, which can be overlaid on the frequency bandused by existing wireless systems. Further, because of its wide bandcharacteristic, the ultra wide band transmission scheme is highlyprospective as an ultra high-speed wireless transmission technology of100 Mbps level for use in the personal area network (PAN).

On the other hand, in the UWB wireless transmission, if it is assumedthat two or more UWB wireless networks uncoordinated to each other existin a same area, each network performs communication at a low signalpower density by use of overlapping ultra wide band occupied bands, sothat a heavy interference may be caused depending on the positionalrelationships of the transmitting and receiving apparatuses. When thewireless communication scheme according to the present embodiment isapplied to the UWB wireless transmission, no resource overlapping iscaused to effectively avoid interference, thereby allowing performingthe UWB wireless transmission without causing the networks todisturbance each other.

In the above-mentioned embodiment, there are three MSs, which are theslaves of the BS and two MSs, which are the slaves of the MS-A. It willbe apparent that the present invention is not limited to thisconfiguration. The communication terminals MS-D and MS-E may also havethe wireless base station capabilities and configure a grandchildnetwork within a scope of the resources assigned to the own apparatus,thereby recursively assigning the resources to the slave communicationterminals.

In the above-mentioned embodiment, in the state where the communicationterminal MS-A is configuring a daughter network with its slavecommunication terminals, the communication terminals MS-B and MS-C mayalso have the wireless base station capabilities to concurrentlyconfigure their daughter networks within a scope of the resourcesassigned to these communication terminals MS-B and MS-C. In this case,the resource scopes of these daughter networks do not overlap either, sothat no disturbance takes place between the daughter networks.

B. The Second Embodiment

Referring to FIG. 5, there is shown the existence of two personal areanetworks spaced from each other. In what follows, a small-scale personalarea network is also called a “piconet.”

In the figure, the first piconet 1 is constituted by a first controlstation 11 called a coordinator and a plurality of wirelesscommunication apparatuses 12, 13, 14, and so on which constitute thefirst piconet 1. The second piconet 2 is constituted by a second controlstation 21 called a coordinator and a plurality of wirelesscommunication apparatuses 22, 23, and so on, which constitute the secondpiconet 2.

The service area of each of the first piconet 1 and the second piconet 2is a range of radio transmitted from the control station (indicated bydashed lines). Therefore, it will be understood that the first piconet 1and the second piconet 2 exist on the same frequency channel withoutspatially interfering each other.

Referring to FIG. 6, there is shown a state in which the first piconet 1and the second piconet 2 exist in a spatially overlapping manner.

In the figure, the service area of each of the first piconet 1 and thesecond piconet 2 is a range of radio transmitted from the controlstation (indicated by dashed lines). Therefore, it will be understoodthat the service areas of the first piconet 1 and the second piconet 2are spatially overlapping each other.

In the case shown in FIG. 6, if the first piconet 1 and the secondpiconet 2 exist on a same frequency channel, the information can bereceived from the other piconet. If the first piconet 1 and the secondpiconet 2 independently perform guaranteed time slot transmission of thesame time, a problem of the collision of the information about bothpiconets occurs.

In order to overcome this problem, the second embodiment of theinvention provides a scheme by which the control stations (orcoordinators) 11 and 12 of the first piconet 1 and the second piconet 2perform communication so that the collision between the control stationsin these piconets is avoided as indicated by the bi-directional arrowsshown. For example, one piconet understands the state of guaranteed timeslot of the other piconet from the beacon information and sets the timeused for information transmission by the other piconet as an unassignedarea of the own piconet, thereby allowing the coexistence of bothpiconets on a same frequency channel for piconet operation.

Referring to FIG. 7, there is shown a configuration of a transmissionframe for use in the piconets associated with the present embodiment.

In the figure, a transmission frame 30 is constituted by a beaconbroadcast area (B) 31 in which a beacon is broadcast from the controlstation to the network at the beginning of the frame, a content accessperiod (CAP) 32 in which information about the processing to be executedwhen getting into the network for example is exchanged, and a contentionfree period (CFP) 33 in which each wireless communication apparatusperforms guaranteed time slot for information transmission. A period upto a next network broadcast area is provided as one transmission frameperiod.

The configuration inside of the transmission frame is written in thebeacon information, which is broadcast onto the network at the beginningof the frame.

It should be noted that, in accordance with the specificationsstandardized by the IEEE 802.15.3, the time slot assignment transmissionby the guaranteed time slot (GTS) 34 is directly performed between anywireless communication apparatuses in the wireless network 1 inaccordance with a multiplex transmission method called dynamic TDMA(Time Division Multiple Access) in the contention free period 23.

Referring to FIG. 8, there is shown a schematic diagram of aconfiguration of a wireless communication apparatus 10, which operatesin the piconet associated with the present embodiment. As shown, thewireless communication apparatus 10 is constituted by an interface 61,an interface buffer 62, a wireless buffer 63, a wireless communicationsection 64, an antenna 65, a control section 67, and an informationstorage section 68.

The interface 61 connects the wireless communication apparatus 10 toexternal equipment such as a personal computer (PC). The interfacebuffer 62 holds media information 601 received from external equipment.The wireless buffer 63 holds information 602 for wireless transmissionreceived from the interface buffer 62 as a wireless transmission packet.

The control section 67 controls the sequence of data transmissionprocessing in the wireless communication apparatus 10 in a centralizedmanner. Namely, in response to a notification 603 for wirelesstransmission, the control section 67 stores a reservation request 604 inthe wireless buffer 63 of wireless transmission if guaranteed time slottransmission is required and sends this request to a control station10-8 by use of the contention access period (CAP) in the transmissionframe. Namely, in this configuration, the reservation request 605 fortransmission is wirelessly transmitted from the antenna 65 via thewireless communication section 64.

A signal received by the wireless communication apparatus 10 is suppliedto the wireless communication section 64 via the antenna 65 to be sentto the wireless buffer 63 as a decoded signal 611.

Further, if a signal is received by the wireless communication apparatus10, which provides a control station, the received signal is supplied tothe control section 67 as a control signal 612. The control section 67determines whether the signal is a reservation request from anotherwireless communication apparatus constituting the piconet. The time slotassignment information based on this decision is constituted as a beaconsignal, and is wirelessly transmitted at the beginning of the frameperiod (refer to FIG. 7). Namely, the beacon signal 605 of that frame iswirelessly transmitted into the piconet from the antenna 65 via thewireless communication section 64.

Receiving the beacon signal from the other piconet, the wirelesscommunication apparatus 10 can analyze the beacon information by thecontrol section 67 and set the area, which affects the informationtransmission of the other piconet, as an unassigned area in the ownpiconet.

The beacon signal 605 including the specification of such an unassignedarea is wirelessly transmitted into the piconet from the antenna 65 viathe wireless communication section 64.

In wireless transmitting apparatus other than the control station in thepiconet, when the beacon information transmitted from the controlstation almost periodically is received, the control section 67 confirmsthe corresponding guaranteed time slot assignment information of thecontention free period (CFP) described in this beacon information andsets wireless communication section 64 in accordance with theinstruction specified in the assignment information, therebytransmitting the wireless transmission packet stored in the wirelessbuffer 63.

If the reception in the contention free period (CFP) is not specified inthe beacon information transmitted from the control station, eachwireless transmission apparatus other than the control station sets thewireless communication section 64 in accordance with that instruction toperform signal reception in a predetermined times relation. The receivedinformation 611 is held in the wireless buffer 63. Then, the controlsection 67 reconstructs the information 614 received on a frame periodbasis in accordance with the frame period signal 604 and passes thereconstructed information to the interface buffer 62. The interface 61passes the received information to external equipment (not shown) aspredetermined interface format information 615.

The above-mentioned sequence of control operations is performed asinstructed by the control section 67. The control section 67 has theinformation storage section 68 for storing various transmission controlprograms and control information. In order to reference these pieces ofinformation from time to time, the control section 67 specifies acommand group 616 with the information storage section 68.

Referring to FIG. 9, there is shown an example of an operation sequenceto be performed between the first control station 11 of the firstpiconet 1 and the control station 21 of the second piconet 2. To be morespecific, FIG. 9 shows a procedure of setting unassigned areas in thefirst piconet 1 and the second piconet 2 while receiving the beaconinformation by the control station 11 of the first piconet 1 and thecontrol station 21 of the second piconet 2. In the example shown, it isassumed that the control station 11 and the control station 21 of thefirst piconet 1 and the second piconet 2 operate as equals by followingthe processing procedure shown in FIG. 14. It is also assumed that, ineach piconet, a certain wireless communication apparatus is set as acontrol station by following a predetermined process.

First, the first control station 11 of the first piconet 1 sends beaconinformation of the first piconet 1 (P1).

The control station 21 of the second piconet 2 cannot receive thisbeacon information. For example, if the first piconet 1 and the secondpiconet 2 are separated enough, each cannot receive the beaconinformation of the other. In such a case, piconets are formedindependently of each other (refer to FIG. 5).

Next, the control station 21 of the second piconet 2 sends the beaconinformation of the second piconet 2 (P2).

If the first piconet 1 and the second piconet 2 are close enough to eachother, the beacon information of the other can be received (refer toFIG. 6). When the beacon information from the control station 21 isreceived, the control station 11 of the first piconet 1 sets theunassigned area for the second piconet 2.

Then, the control station 11 of the first piconet 1 sends the beaconinformation of the first piconet 1, which includes the setting of theunassigned area (P3).

If the beacon information from the control station 11 is received, thecontrol station 21 of the second piconet 2 sets an unassigned area forthe first piconet 1.

Next, the control station 21 of the second piconet 2 sends the beaconinformation of the second piconet 2, which includes the setting of theunassigned area (P4).

Thus, while operating as equals, the control station 11 and the controlstation 21 of the first piconet 1 and second piconet 2 allow thecoexistence of a plurality of piconets on the same frequency channel byperforming time division multiplexing on them. Obviously, in the UWBwireless communication scheme in which data are spread over an extremelywide frequency band, a plurality of piconets can be made coexist byperforming the above-mentioned time slot assignment.

Then, if the control station 11 of the first piconet 1 cannot receivethe beacon information of the second piconet 2 because of a dynamicchange in the communication environment (for example, the movement ofthe wireless communication apparatus) (P5), the control station 11 ofthe first piconet 1 can clear the setting of this unassigned area.

Likewise, if the control station 21 of the second piconet 2 cannotreceive the beacon information of the first piconet 1 (P6), the controlstation 21 of the second piconet 2 can clear the setting of theunassigned area.

FIGS. 10 through 13 show the processes of setting unassigned areas byeach of the first piconet 1 and the second piconet 2 in terms of thetransmission frame configurations of the first piconet 1 and the secondpiconet 2.

At the stage shown in FIG. 10, neither the first piconet 1 nor thesecond piconet 2 sets an unassigned area, but each is operating byindividually performing GTS assignment in its CFP area. Therefore, innone of the transmission frames of the first piconet 1 and the secondpiconet 2, the unassigned area for the other piconet is not set.

At the stage shown in FIG. 11, the control station 11 of the firstpiconet 1 receives the beacon information of the second piconet 2 andsets, to the transmission frame of the first piconet 1, the unassignedarea for the second piconet 2.

In the example shown, the first piconet 1 performs the GTS assignment inthe own piconet in the CFP area in a concentrated manner and, byminimizing the length of the CAP area, sets a half of the frame periodas an unassigned area.

At the stage shown in FIG. 12, the control station 21 of the secondpiconet 2 receives the beacon information of the first piconet 1 andsets the unassigned area for the first piconet 1 in the transmissionframe of the second piconet 2.

In the example shown, the control station 21 of the second piconet 2performs the GTS assignment in the CFP area in a concentrated mannerexcept for the portion equivalent to the unassigned area of the firstpiconet 1. In addition, the control station 21 minimizes the length ofthe CAP area and sets the area for use by the first piconet 1 as theunassigned area.

A the stage shown in FIG. 13, in response to that the first piconet 1and the second piconet 2 do not receive the beacon information of eachother, the setting of the unassigned area in each piconet is cleared.

In the example shown, each of the first piconet 1 and the second piconet2 uses the entire frame period for its piconet transmission, so that theGTS assignment in the CFP area is made in a redundant manner and the CAParea is set longer for an enough margin.

In the examples shown in FIGS. 9 through 13, the control stationsoperate as equals to each other, so that two piconets using a samefrequency channels can coexist. Obviously, the equal operation of eachcontrol station makes it practical for three or more piconets using asame frequency channel to coexist.

Referring to FIG. 14, there is shown a flowchart describing theprocessing operation of each of the control stations constitutingpiconets for realizing the operation sequence shown in FIG. 9. Actually,this processing operation is realized by the control section 67 in thewireless communication apparatus 10 set as a control station byexecuting predetermined program codes.

In step S1, it is determined whether the wireless communicationapparatus is operating as the control station. It is assumed that, ineach piconet, a certain wireless communication apparatus have become thecontrol station by following a predetermined process. However, theprocedure itself for setting the control station in each piconet is notdirectly associated with the key concept of the present invention, sothat the description of this procedure is skipped.

If the wireless communication apparatus is not the control station, thedecision of decision block S1 is No and therefore this processingroutine comes to an end. On the other hand, if the wirelesscommunication apparatus is found operating as the control station, thenit is determined in step S2 whether the beacon information of the otherpiconet existing around has been received.

If the beacon information of the other piconet is found not received,then the decision of decision block S2 is No, so that this processingroutine comes to an end. On the other hand, if the beacon information ofthe other piconet is found received, then the frame structure of thatpiconet is confirmed on the basis of the received beacon information instep S3.

In step S4, it is determined whether the unassigned area for the ownpiconet is set.

If the unassigned area is found set, then this unassigned area is set asan area for use by the own piconet in step S9 and then the proceduregoes to step S10.

On the other hand, if the unassigned area is found not set, it isdetermined in step S5 whether GTS assignment of contention free period(CFP) is duplicated with the other piconet existing around.

If GTS assignment is found duplicate with the other piconet, then theGTS assignment of the own piconet is changed in step S6. If the GTSassignment is found not duplicate, the process of step S6 is skipped.

In step S7, it is determined whether there is GTS assignment in beacontransmitting time.

If GTS is found assigned to the beacon transmitting time, then thebeacon transmission time is adjusted in step S8 so that the assignmentof the own piconet will not overlap the assignment of the other piconetand then the procedure goes to step S10. If the GTS is not foundassigned to the beacon transmitting time, the process of step S8 isskipped and procedure goes to step S10.

In step S10, the unassigned area of the own piconet is set. In step S11,The modification of the frame structure is broadcast into the piconet asthe beacon information.

Thus, in the present embodiment, the control stations of the piconetsoperate as equals to each other to perform the operation sequence shownin FIG. 9, thereby allowing the coexistence of a plurality of piconetsusing a same frequency channel without interfering each other.

In the UWB wireless transmission, if two or more UWB wireless networks,which are uncoordinated with each other, exist in a same area, eachnetwork performs communication at a low signal power density by use ofan overlapping ultra wide band occupied band, so that a heavyinterference may be caused depending on the positional relationshipbetween the receiving/transmitting apparatuses. On the contrary, if thewireless communication scheme associated with the present invention isapplied to UWB wireless networks, no resource duplication occurs, sothat the interference can be effectively avoided to allow the wirelesstransmission between the networks without disturbance.

C. The Third Embodiment

In the above-mentioned second embodiment, a plurality of piconetsoperate as equals to each other and the control station of each piconetexecutes the same processing procedure, thereby allowing the pluralityof piconets using a same frequency channel to coexist withoutinterfering each other.

In the third embodiment of the invention, a plurality of piconets usinga same frequency channel realize coexistence without interfering eachother while forming a parent and daughter relationship among them.Namely, the parent piconet assigns a time slot for use for the daughterpiconets and the daughter piconets use the time slot assigned by theparent piconet to perform time slot assignment or GTS assignment betweenthe daughter piconets.

In order to establish a parent and daughter relationship between two ormore piconets, the control station of each daughter piconet onceparticipates in the parent piconet as a normal terminal station toperform a time slot request operation like other terminal stations inthe parent piconet and recursively operate the control stationcapabilities to assign the time slot obtained in the parent piconet toeach of terminal stations in the daughter piconets. Obviously, some ofthe terminal stations in each daughter piconet may construct grandchildpiconets by likewise realizing the recursive control stationcapabilities.

Also, the control station of the parent piconet may assign time slots(or the parent piconet may prepare an unassigned area) in response to atime slot request from the control station of each daughter piconetregardless of the procedure for participation between the piconets,thereby realizing the coexistence of the piconets without interferencetherebetween.

Consequently, according to the present embodiment, if a network to whichno time slot is assigned occurs in such a case as when a new network isconstructed in the same space or a network has moved thereto fromanother space, the problem of network contention may be solved tosuitably perform the dynamic assignment of time slots (or resources). Inaddition, an existing network may assign resources to a network newlyappearing in the same space.

In the case where a parent and daughter relationship is formed betweenpiconets to avoid the interference therebetween as with the presentembodiment, the processing operations to be executed by the wirelesscommunication apparatus are different depending on for which of thecontrol station for the parent piconet and the daughter piconetfunctions, unlike the above-mentioned second embodiment (which will bedescribed later).

Referring to FIG. 15, there is shown an example of an operation sequencefor realizing the coexistence of two piconets using a same frequencychannel without interfering each other while forming a parent anddaughter relationship. In the example shown, it is assumed that thereare piconet A and piconet B, both independently operating a networkwithout forming a parent and daughter relationship in advance.

First, it is assumed that the control station of piconet B could receivethe beacon of piconet A (P11).

Consequently, the control station of piconet B sends a participationrequest to the control station of piconet A (P12). In response, thecontrol station of piconet A returns a participation approval to thecontrol station of piconet B (P13). The participation approval isperformed by the assignment of a network address and its return forexample. As a result, a parent relationship is formed between piconet Aand piconet B.

Then, the control station of the piconet B sends a time slot request (ora channel time request) to the control station of piconet A (P14). Inresponse, the control station of piconet A returns a time slotassignment to the control station of piconet B (P15). At this time, thecontrol station of piconet A may send the time slot assignment by adirect frame or by a beacon written with a time slot assignment result.

The time slot assignment is returned in a method in which the controlstation of piconet A notifies, within piconet A, a beacon written withthe time slot assignment in piconet A, for example. Alternatively, thecontrol station of piconet A may directly send a transmission framewritten with time slot assignment information to the control station ofpiconet B (a direct frame). In the latter, the control station ofpiconet B may confirm the reception of the transmission frame to thecontrol station of piconet A (P16).

The control station of piconet A notifies the beacon within piconet A(P17). The beacon indicates the information that time slot assignment ismade for piconet B. Therefore, piconet B may operate piconet B by use ofthe assigned time slot.

Consequently, if piconet B is newly constructed in a same space in whichpiconet A exists or piconet B has moved to the same space, the problemof contention inside piconet A can be solved to dynamically assign thetime slot (or resources) for operating piconet B.

The control station of piconet B notifies the beacon written with theoperation of piconet B within piconet B (P18). Further, thecommunication apparatus built in piconet B can request the controlstation of piconet B for a time slot assignment (P19). In response, thecontrol station of piconet B reassigns a portion of the time slotassigned by piconet A before to notify it by the direct frame forexample (P20). The communication apparatus of piconet B may return areception confirmation (P21).

In UWB wireless transmission, if two or more uncoordinated UWB wirelessnetworks exist in a same area, each network performs communication at alow signal power density by use of an overlapping ultra wide bandoccupied band, so that, depending on the positional relationship betweenreceiving/transmitting apparatuses, a heavy interference occurs. If theoperation sequence between piconets shown in FIG. 15 is applied to theUWB wireless communication scheme, no resource overlapping occurs, sothat the interference may be effectively avoided, thereby allowing UWBwireless transmission without interference between networks.

Referring to FIG. 16, there is shown a flowchart describing a processingprocedure of the control station for realizing the coexistence ofpiconets by avoiding the interference therebetween while forming aparent and daughter relationship therewith. Actually, this processingoperation is realized by the control section 67 of the wirelesscommunication apparatus 10 by executing predetermined program codes.

First, the existence of an adjacent piconet is detected by receiving abeacon signal from an adjacent station for example (step S21).

If the beacon signal has been received from an adjacent station, it isattempted to participate in this existing adjacent piconet as a daughterpiconet. In this case, the address information of the adjacent stationpiconet is obtained from this beacon information (step S22).

Next, the obtained address information is compared with the addressinformation of the own station to determine whether the address of theown station is newer (step S23). If the address of the own station foundnewer, the participation request is sent to the control station of theadjacent piconet (step S24) and determines whether the participationapproval from the adjacent piconet has been received (step S25). Uponreception of the participation approval (step S25), the operation ofparticipating into this adjacent piconet is completed. As a result, thedaughter piconet can be constructed with the adjacent piconet being theparent piconet. Subsequently, the transmission time slot necessary forthe own station piconet may be estimated.

Next, a time slot request is sent to the control station of the adjacentpiconet, which is the parent piconet (step S26). If a time slotassignment comes from that control station (step S27), the receptionconfirmation is returned to that control station (step S28).

Subsequently, the operation of the piconet of the own station is enabledon the assigned time slot (step S29). Thereafter, when a time slotassignment request from the communication station of the piconet of theown station occurs, the communication may be performed by reassigningthis assigned time slot.

Subsequently, the operation of the piconet of the own station is enabledon the assigned time slot (step S29). Thereafter, when a time slotassignment request from the communication station of the piconet of theown station occurs, the communication may be performed by reassigningthis assigned time slot.

On the other hand, if no beacon signal has been received from theadjacent station in step S21 or the address of the own station obtainedfrom the adjacent piconet is found not newer in step S23, then thepossibility for the own station to operate as the parent piconet isdetermined. Namely, whether a participation request from the adjacentstation has been received or not is determined (step S30).

When a participation request has been received from the adjacentstation, the adjacent station is made participate in the own stationnetwork and an address is assigned to the adjacent station and aparticipation approval is sent thereto (step S31). This participationapproval includes the address assigned to the adjacent station.

Next, when a time slot request has been received from this adjacentstation (step S32), it is determined whether the assignment of the timeslot request is practicable (step S33). If the time slot assignment isfound practicable, the time slot assignment is sent to that adjacentstation (step S34).

Subsequently, the piconet of the own station is operated in an areaother than the assigned time slot (step S35).

In the example shown in FIG. 16, a parent and daughter relationship isformed on the basis of the address information of the control station inaddition to the sequence in which the piconets are constructed. For thisaddress, the identification information unique to equipment (physical),such as MAC (Machine Control Access) address for example is used. Inthis case, the new address denotes a new model. Therefore, forming aparent and daughter relationship between piconets in accordance with theaddress information can set the wireless communication apparatus havingthe old address to the parent piconet and, at the same time, recursivelyconstruct daughter piconets by the wireless communication apparatuseshaving more up-to-date control station capabilities. The control stationof the parent piconet may not necessarily sense the existence ofdaughter piconets in the same space.

Referring to FIG. 17, there is shown another example of an operationsequence for realizing the coexistence of two piconets by avoiding theinterference therebetween while forming a parent and daughterrelationship therewith. It is assumed that, in the parent piconet andthe daughter piconet, the network is operated with the transmissionframe period having the structure shown in FIG. 7.

From the control station of the parent piconet, a beacon signal of theparent piconet is sent to the daughter piconet in a predetermined period(P31).

On the side of the control station of the daughter piconet, whenconstructing the daughter piconet, a time slot assignment request (anunassigned GTS) is sent as the daughter piconet's construction requestin the contention access period (CAP) of the parent piconet (P32).

If a time slot assignment request has been received from the daughterpiconet, the control station of the parent piconet sets the unassignedarea for the daughter piconet because a daughter piconet constructionrequest has been received and transmits a next parent piconet beaconsignal including the unassigned area information, thereby notifying theunassigned GTS (P33).

Receiving the parent piconet beacon signal including the unassigned areainformation, the control station of the daughter piconet startsoperating the daughter piconet in that unassigned area, transmitting adaughter piconet beacon signal (P34). At this moment, the area that isused for the transmission of the parent piconet is set as an unassignedarea on the side of the daughter piconet.

Further, receiving the daughter piconet beacon signal, the controlstation of the parent piconet may use its own unassigned area to knowthat the daughter piconet has been formed.

Thus, if the daughter piconet appears in the state with no time slotassigned at all in such a case as when the daughter piconet is newlyconstructed in a same space of the parent piconet or the daughterpiconet has moved from another space into the parent piconet, theproblem of the contention between networks can be resolved to suitablyperform the dynamic assignment of a time slot (or resources). Inaddition, the parent network can assign resources to any other networkthat newly appears in the same space.

Subsequently, the beacon signal of the parent piconet is transmitted byuse of the unassigned area of the daughter piconet (P35).

In UWB wireless transmission, if two or more uncoordinated UWB wirelessnetworks exist in a same area, each network performs communication at alow signal power density by use of an overlapping ultra wide bandoccupied band, so that, depending on the positional relationship betweenreceiving/transmitting apparatuses, a heavy interference occurs. If theoperation sequence between piconets shown in FIG. 17 is applied to theUWB wireless communication scheme, no resource overlapping occurs, sothat the interference may be effectively avoided, thereby allowing UWBwireless transmission without disturbance between networks.

Referring to FIG. 18, there is shown a flowchart describing a processingprocedure of the control station of the parent piconet for realizing thecoexistence of piconets by avoiding the interference therebetween inaccordance with the operation procedure between piconets shown in FIG.17. Actually, this processing operation is realized by executingpredetermined program codes by the control section 67 of the wirelesscommunication apparatus 10, which operates as the control station of theparent piconet.

First, in step S41, it is determined whether the wireless communicationapparatus itself is operating as the control station.

If the wireless communication apparatus is found operating not as thecontrol station, then the decision is No in step S41, upon which thisprocessing routine comes to an end. If the wireless communicationapparatus is found operating as the control station, it is determined instep S42 whether a daughter piconet construction request has beenreceived.

If the daughter piconet construction request has not been received, thedecision of step S42 is No, upon which this processing routine comes toan end. If the daughter piconet construction request has been received,then the information about the transmission time slot (the time)necessary for the piconet is obtained in step S43.

In step S44, it is determined whether it is practicable to set thecorresponding transmission time slot as an unassigned area in the parentpiconet.

If the unassigned area cannot be set, the decision in step S44 is No,upon which this processing routine comes to an end. If the unassignedarea can be set, then it is determined in step S45 whether a change isnecessary to the existing time slot assignment.

If the change is necessary, then the time slot assignment in the parentpiconet is changed in step S46. If the change is not necessary, theprocess of step S46 is skipped.

In step S47, the unassigned area is set in the parent piconet. In stepS48, this setting is transmitted as the beacon information of the parentpiconet, upon which this processing routine comes to an end.

Referring to FIG. 19, there is shown a flowchart describing a processingprocedure of the control station of the daughter piconet for realizingthe coexistence of piconets by avoiding the interference therebetween inaccordance with the operation procedure executed between the piconetsshown in FIG. 17. Actually, this processing operation is realized by thecontrol section 67 of the wireless communication apparatus that operatesas the control station of the daughter piconet by executingpredetermined program codes.

First, in step S51, on a basis of user instruction for example, it isdetermined whether the wireless communication apparatus has received aninstruction for operating as the control station.

If the wireless communication apparatus has not received theinstruction, the decision block S51 is No, upon which this processingroutine comes to an end. If the wireless communication apparatus hasreceived the instruction, is determined in step S52 whether a beaconsignal of the parent piconet has been received.

If the wireless communication apparatus has not received the beaconsignal from the parent piconet, the decision block S52 is No and thewireless communication apparatus operates as the control station of anordinary piconet in step S53 to transmit a beacon signal, upon whichthis processing routine comes to an end.

If the wireless communication apparatus has received the beacon signalfrom the parent piconet, then a transmission time slot (or time)necessary for the daughter piconet is estimated in step S54. In stepS55, the daughter piconet construction request is transmitted in thecontention access period (CAP) in the parent piconet.

In step S56, the beacon of the parent piconet is received to determinewhether the setting of an unassigned area has been performed.

If the setting of an unassigned area has not been performed, thedecision block S56 is No and the procedure returns to step S54, in whichthe transmission time slot necessary for the daughter piconet isestimated again, transmitting a daughter piconet construction request tothe parent piconet.

On the other hand, if the setting of the unassigned area in the parentpiconet has been confirmed, then the setting of an unassigned area inthe daughter piconet is performed in step S57.

In step S58, the setting of the unassigned area is sent as the beaconinformation of the daughter piconet, upon which this processing routinecomes to an end.

Supplement:

While the preferred embodiments of the present invention have beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the appendedclaims.

While the preferred embodiments of the present invention have beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the appendedclaims.

INDUSTRIAL APPLICABILITY

As described, the present invention describes an excellent wirelesscommunication system which allows the coexistence of a plurality ofwireless networks contending each other on a same frequency band,excellent wireless communication control apparatus and wirelesscommunication control method which allow the suitable control of thecommunication operation in each of a plurality of wireless networkscontending each other on a same frequency band, and an excellentcomputer program supporting these capabilities.

As described, the present invention provides an excellent wirelesscommunication system, excellent wireless communication control apparatusand wireless communication control method, and an excellent computerprogram which allow the coexistence of a plurality of personal areanetworks on a same frequency channel by time-division-multiplexing atransmission frame period only by performing control betweentransmission apparatuses providing control stations.

As described, the present invention provides an excellent wirelesscommunication system, an excellent wireless communication controlapparatus and wireless communication control method, and an excellentprogram which, when a new network has been constructed in a same spaceor a network has moved thereto from another space for example, allow tosolve the problem of the contention between networks, thereby suitablyperforming the dynamic assignment of time slots (or resources).

As described and according to the invention, beacon signals aretransferred between the control stations existing on a same channel,which allows to understand the frame structure of the destinationnetwork, thereby changing the time slot assignment so as to avoid thecollision with the guaranteed time slot of the own network from thestatus of the guaranteed time slot.

As described and according to the invention, on the basis of theguaranteed time slot status, an area to be used for the transmission bythe destination network may be set as an unassigned area of the ownnetwork, thereby realizing the transmission which avoids the collisionwith the information of the destination network.

As described and according to the invention, if an unassigned area isset on the destination network, this unassigned area may be set as anarea for use by the own network for transmission, thereby making aplurality of networks coexist on a same channel.

If the control station of the own network does not receive a beaconsignal from the destination network, the above-mentioned setting of theunassigned area may be cleared, thereby realizing a method ofeffectively using a same channel by the own network.

Alternatively, one control station may issue a network constructionrequest to the other control station, thereby performing time slotassignment between the networks. The construction request to the othercontrol station includes a participation request for participating inthe network and a time slot request for requesting the other controlstation for time slot assignment.

As described above and according to the invention, the communicationterminals under the control of the wireless base station in the parentnetwork recursively have the wireless base station capabilities and,within a resource scope of the own apparatus assigned to the wirelessbase station, assign resources to an other communication terminals underthe control of the wireless base station, thereby allowing to configuretwo or more networks which are guaranteed not to disturb each other.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

In the drawings:

FIG. 1

-   PARENT NETWORK-   DAUGHTER NETWORK    FIG. 2-   112 RADIO RECEIVING SECTION-   113 DEMODULATING SECTION-   →RECEIVING DATA-   114 REQUEST CONFIRMING SECTION-   115 SCHEDULER-   115 BEACON INSERTING SECTION-   ←TRANSMITTING DATA-   117 MODULATING SECTION-   118 RADIO TRANSMITTING SECTION    FIG. 3-   122 RADIO RECEIVING SECTION-   123 DEMODULATING SECTION-   →RECEIVING DATA-   124 BEACON CAPTURING SECTION-   125 REQUEST CONFIRMING SECTION-   15 SCHEDULER-   127 COMMUNICATION CONTROL SECTION-   128 BEACON INSERTING SECTION-   ←TRANSMITTING DATA FOR DAUGHTER NETWORK-   129 FRAME CONFIGURING SECTION-   ←TRANSMITTING DATA FOR PARENT NETWORK-   ↓TRANSMISSION REQUEST SIGNAL-   130 MODULATING SECTION-   131 RADIO TRANSMITTING SECTION    FIG. 4-   From above, from left-   TDMA FRAME-   PARENT NETWORK BEACON USER A USER B USER C-   CONTENTION PARTITION-   DAUGHTER NETWORK BEACON USER D USER E CONTENTION PARTITION    FIG. 5-   From left-   FIRST PICONET 1-   SECOND PICONET 2    FIG. 6-   From above, from left-   FIRST PICONET 1-   SECOND PICONET 2-   COMMUNICATION BETWEEN PICONETS    FIG. 7-   34 GUARANTEED TIME SLOT-   31 BEACON-   32 CONTENTION ACCESS PERIOD-   33 CONTENTION FREE PERIOD-   →TIME-   30 TRANSMISSION FRAME PERIOD    FIG. 8-   61 INTERFACE-   62 INTERFACE BUFFER-   63 WIRELESS BUFFER-   64 WIRELESS COMMUNICATION SECTION-   67 CONTROL SECTION-   68 INFORMATION STORAGE SECTION-   65 ANTENNA-   10 WIRELESS COMMUNICATION APPARATUS    FIG. 9-   From above, from left-   CONTROL STATION 11 OF FIRST PICONET 1-   CONTROL STATION 21 OF SECOND PICONET 2-   BEACON INFORMATION OF FIRST PICONET (P1)-   (RECEPTION DISABLED)-   BEACON INFORMATION OF SECOND PICONET (P2)-   SET UNASSIGNED AREA FOR SECOND PICONET-   BEACON INFORMATION OF FIRST PICONET (P3)-   SET UNASSIGNED AREA FOR FIRST PICONET-   BEACON INFORMATION OF SECOND PICONET (P4)-   CLEAR UNASSIGNED ARE FOR SECOND PICONET-   BEACON INFORMATION OF SECOND PICONET (P5)-   (RECEPTION DISABLED)-   BEACON INFORMATION OF FIRST PICONET (P6)-   (RECEPTION DISABLED)-   CLEAR UNASSIGNED AREA FOR FIRST PICONET    FIG. 10-   From above, from left-   FRAME PERIOD N OF FIRST PICONET-   FIRST PICONET-   CONTENTION FREE PERIOD (CFP)-   SECOND PICONET-   CONTENTION FREE PERIOD (CFP)-   FRAME PERIOD OF SECOND PICONET-   FRAME PERIOD OF SECOND PICONET    FIG. 11-   From above, from left-   FRAME PERIOD N OF FIRST PICONET-   FIRST PICONET-   CONTENTION FREE PERIOD (CFP)-   UNASSIGNED AREA-   SECOND PICONET-   CONTENTION FREE PERIOD (CFP)-   FRAME PERIOD OF SECOND PICONET-   FRAME PERIOD OF SECOND PICONET    FIG. 12-   From above, from left-   FRAME PERIOD N OF FIRST PICONET-   FIRST PICONET-   CONTENTION FREE PERIOD (CFP)-   UNASSIGNED AREA-   SECOND PICONET-   CONTENTION FREE PERIOD (CFP)-   CONTENTION FREE PERIOD (CFP)-   UNASSIGNED AREA-   FRAME PERIOD OF SECOND PICONET-   FRAME PERIOD OF SECOND PICONET    FIG. 13-   From above, from left-   FRAME PERIOD N OF FIRST PICONET-   FIRST PICONET-   CONTENTION FREE PERIOD (CFP)-   SECOND PICONET-   CONTENTION FREE PERIOD (CFP)-   CONTENTION ACCESS PERIOD (CAP)-   FRAME PERIOD OF SECOND PICONET-   FRAME PERIOD OF SECOND PICONET    FIG. 14-   CONTROL STATION PROCESSING-   S1 OPERATING AS CONTROL STATION?-   S2 BEACON OF ANOTHER PICONET RECEIVED?-   S3 CHECK FRAME STRUCTURE FROM OTHER PICONET INFORMATION.-   S4 UNASSIGNED AREA SET TO OWN PICONET?-   S5 DUPLICATE ASSIGNMENT WITH ANOTHER PICONET?-   S6 CHANGE GTS ASSIGNMENT OF OWN PICONET.-   S7 ASSIGNED TO BEACON TRANSMITTING TIME?-   S8 ADJUST BEACON TRANSMITTING TIME.-   S9 USE THAT UNASSIGNED AREA BY OWN PICONET.-   S10 SET UNASSIGNED AREA OF OWN PICONET.-   S11 SEND BEACON INFORMATION ADDRESSED TO OWN PICONET.    FIG. 15-   From above, from left-   PICONET A COMMUNICATION APPARATUS-   PICONET A CONTROL STATION-   PICONET B CONTROL STATION-   PICONET B COMMUNICATION APPARATUS    -   BEACON OF PICONET A P11    -   REQUEST TO PARTICIPATE P12    -   REQUEST TO APPROVE P13    -   REQUEST TIME SLOT P14    -   ASSIGN TIME SLOT P15    -   CONFIRM RECEPTION P16    -   BEACON OF PICONET A P17    -   BEACON OF PICONET B P18    -   REQUEST TIME SLOT P19    -   ASSIGN TIME SLOT P20    -   CONFIRM RECEPTION P21    -   BEACON OF PICONET A P17    -   BEACON OF PICONET B P18        FIG. 16-   OPERATION OF ADJACENT PICONET CONTROL STATION-   S21 BEACON OF ADJACENT STATION RECEIVED?-   S22 GET ADDRESS INFORMATION OF ADJACENT STATION PICONET.-   S23 OWN STATION ADDRESS NEW?-   S24 SEND REQUEST TO PARTICIPATE TO ADJACENT STATION.-   S25 PARTICIPATION APPROVAL RECEIVED?-   S26 SEND TIME SLOT REQUEST TO ADJACENT STATION PICONET.-   S27 TIME SLOT ASSIGNMENT RECEIVED FROM ADJACENT STATION?-   S28 SEND RECEPTION CONFIRMATION TO ADJACENT STATION.-   S29 OPERATE OWN STATION'S PICONET BY ASSIGNED TIME SLOT.-   S30 PARTICIPATION REQUEST RECEIVED FROM ADJACENT STATION?-   S31 SEND PARTICIPATION APPROVAL TO THAT ADJACENT STATION.-   S32 TIME SLOT REQUEST RECEIVED FROM ADJACENT STATION?-   S33 TIME SLOT ASSIGNABLE?-   S34 SEND TIME SLOT ASSIGNMENT TO THAT ADJACENT STATION.-   S35 OPERATE OWN STATION'S PICONET BY TIME SLOT OTHER THAN ASSIGNED    TIME SLOT.    FIG. 17-   From above, from left-   PARENT PICONET COMMUNICATION APPARATUS-   PARENT PICONET CONTROL STATION-   DAUGHTER PICONET CONTROL STATION-   DAUGHTER PICONET COMMUNICATION APPARATUS-   BEACON OF PARENT PICONET P31-   CAP AREA-   REQUEST TIME SLOT ASSIGNMENT P32-   REQUEST DAUGHTER PICONET CONSTRUCTION-   REQUEST UNASSIGNED GTS-   BEACON OF PARENT PICONET P33-   REQUEST UNASSIGNED GTS    -   BEACON OF DAUGHTER PICONET P34-   BEACON OF PARENT PICONET P35    FIG. 18-   OPERATION OF PARENT PICONET CONTROL STATION-   S41 OPERATING AS CONTROL STATION?-   S42 DAUGHTER PICONET CONSTRUCTION REQUEST RECEIVED?-   S43 GET TRANSMISSION TIME SLOT NECESSARY FOR DAUGHTER PICONET.-   S44 UNASSIGNED AREA CAN BE SET IN PARENT PICONET?-   S45 NECESSARY TO CHANGE PARENT PICONET'S CFP ASSIGNMENT?-   S46 CHANGE GTS ASSIGNMENT OF PARENT PICONET.-   S47 SET UNASSIGNED AREA IN PARENT PICONET.-   S48 SEND BEACON INFORMATION OF PARENT PICONET.    FIG. 19-   OPERATION OF DAUGHTER PICONET CONTROL STATION-   S51 TO RECEIVE INSTRUCTION FOR OPERATING AS CONTROL STATION?-   S32 BEACON OF PICONET TO BECOME PARENT RECEIVED?-   S53 SEND BEACON INFORMATION AS ORDINARY PICONET.-   S54 ESTIMATE TRANSMISSION TIME SLOT NECESSARY FOR DAUGHTER PICONET.-   S55 SEND DAUGHTER PICONET CONSTRUCTION REQUEST IN CAP AREA OF PARENT    PICONET.-   S56 SETTING OF PARENT PICONET'S BEACON UNASSIGNED AREA CONFIRMED?-   S57 SET UNASSIGNED AREA IN DAUGHTER PICONET.-   S58 SEND BEACON INFORMATION OF DAUGHTER PICONET.    FIG. 20-   901 INFORMATION BIT-   902 SPREAD CODE-   903 SS SIGNAL-   904 TRANSMIT SIGNAL-   905 RECEIVE SIGNAL-   906 DEPREAD CODE-   907 MULTIPLEX SIGNAL-   908 INTEGRAL SIGNAL-   RECEIVED BIT (TO A/D)

1. A wireless communication system, comprising: a plurality of wirelesscommunication apparatuses; and a plurality of wireless networks thatcoexist in a same frequency band, each one of the wireless networksincluding an associated portion of the plurality of wirelesscommunication apparatuses with one of the wireless communicationapparatuses associated with that wireless network operating as a controlstation for that wireless network, the control station of each suchwireless network initially performing time slot assignment within everypredetermined transmission frame period to each one of said wirelesscommunication apparatuses of that wireless network independent of thecontrol stations of the other such networks, the control stations ofeach of said wireless networks comprising: signal detecting means fordetecting a signal from another of said plurality of wireless networks,for detecting address information of the control station of the anotherwireless network from the detected signal, and for comparing the addressinformation of that control station with the address information of thecontrol station of the another wireless network; time slot analyzingmeans for, in response to the address information of that controlstation being newer than the address information of the control stationof the another wireless network, analyzing a transmission time slot onwhich guaranteed time slot transmission is performed in the another ofsaid wireless networks based on a signal detected by said signaldetecting means; and time slot assigning means that, in response to theaddress information of that control station being newer than the addressinformation of the control station of the another wireless network,avoids assigning a transmission time slot on which guaranteed time slottransmission is performed in the another of said wireless networks to awireless communication apparatus in that wireless network.
 2. Thewireless communication system according to claim 1, wherein said timeslot assigning means sets the transmission time slot on which guaranteedtime slot transmission is performed in the another of said wirelessnetworks as an unassigned area in the own wireless network.
 3. Thewireless communication system according to claim 2, wherein said timeslot assigning means clears the setting of the unassigned area in theown wireless network in response to that said signal detecting meansdoes not detect the signal from the another of said wireless networks.4. The wireless communication system according to claim 1, wherein saidtime slot analyzing means analyzes an unassigned area in the another ofsaid wireless networks and said time slot assigning means performs timeslot assignment within the own wireless network by use of saidunassigned area in said another wireless network.
 5. A wirelesscommunication control apparatus in a network environment in which aplurality of wireless networks coexist in a same frequency band, saidwireless communication control apparatus being a control station of oneof said plurality of wireless networks, said wireless communicationcontrol apparatus comprising: signal detecting means for detecting asignal from another of said wireless networks, for detecting addressinformation of the control station of the another wireless network fromthe detected signal, and for comparing the address information of saidwireless communication control apparatus with the address information ofthe control station of the another wireless network, each one of thewireless networks including an associated portion of the plurality ofwireless communication apparatuses with one of the wirelesscommunication apparatuses associated with that wireless networkoperating as a control station for that wireless network, said wirelesscommunication control apparatus and the control station of the anotherwireless network each initially performing time slot assignment withinevery predetermined transmission frame period to each one of saidwireless communication apparatuses of that wireless network independentof the control stations of the other wireless network; time slotanalyzing means for, in response to the address information of saidwireless communication control apparatus being newer than the addressinformation of the control station of the another wireless network,analyzing a transmission time slot on which guaranteed time slottransmission is performed in the another of said wireless networks basedon the signal detected by said signal detecting means; and time slotassigning means which, in response to the address information of saidwireless communication control apparatus being newer than the addressinformation of the control station of the another wireless network,avoids assigning a transmission time slot on which guaranteed time slottransmission is performed on the another of said wireless networks to awireless communication apparatus in that wireless network.
 6. Thewireless communication control apparatus according to claim 5, whereinsaid time slot assigning means sets the transmission time slot on whichguaranteed time slot transmission is performed on the another of saidwireless networks as an unassigned area within that wireless network. 7.The wireless communication control apparatus according to claim 6,wherein said time slot assigning means clears the setting of theunassigned area in that wireless network in response to that said signaldetecting means does not detect the signal from the another of saidwireless networks.
 8. The wireless communication control apparatusaccording to claim 5, said time slot analyzing means analyzes anunassigned area in the another of said wireless networks, and said timeslot assigning means performs time slot assignment within that wirelessnetwork using said unassigned area in said another wireless network. 9.A wireless communication control method, comprising: providing aplurality of wireless communication apparatuses; providing a pluralityof wireless networks that coexist in a same frequency band, each one ofthe wireless networks including an associated portion of the pluralityof wireless communication apparatuses with one of the wirelesscommunication apparatuses associated with that wireless networkoperating as a control station for that wireless network, the controlstation of each such wireless network initially performing time slotassignment within every predetermined transmission frame period to eachone of said wireless communication apparatuses of that wireless networkindependent of the control stations of the other such networks; and forat least one of said wireless networks, detecting a signal from anotherof said wireless networks, detecting address information of the controlstation of the another wireless network from the detected signal,comparing the address information of that control station with theaddress information of the control station of the another wirelessnetwork, and in response to the address information of that controlstation being newer than the address information of the control stationof the another wireless network, analyzing a transmission time slot onwhich guaranteed time slot transmission is performed in the another ofsaid wireless networks based on the signal detected in said signaldetecting step, and avoiding assigning a transmission time slot on whichguaranteed time slot transmission is performed on the another of saidwireless networks to a wireless communication apparatus in that wirelessnetwork.
 10. The wireless communication control method according toclaim 9, wherein said time slot assigning step includes setting thetransmission time slot on which guaranteed time slot transmission isperformed on the another of said wireless networks as an unassigned areawithin that wireless network.
 11. The wireless communication controlmethod according to claim 10, wherein said time slot assigning stepincludes clearing the setting of the unassigned area in that wirelessnetwork in response to that said signal detecting step does not detectthe signal from the another of said wireless networks.
 12. The wirelesscommunication control method according to claim 9, wherein said timeslot analyzing step includes analyzing an unassigned area in the anotherof said wireless networks and said time slot assigning step performstime slot assignment within that wireless network using said unassignedarea in said another wireless network.
 13. A wireless communicationsystem, comprising: a plurality of wireless communication apparatuses;and a plurality of wireless networks that coexist in a same frequencyband, each one of the wireless networks including: an associated portionof the plurality of wireless communication apparatuses with one of thewireless communication apparatuses associated with that wireless networkoperating as a control station for that wireless network, the controlstation of each such wireless network performing time slot assignmentwithin every predetermined transmission frame period to each one of saidwireless communication apparatuses of that wireless network, the controlstation of one such wireless network being a base station, the controlstation of another such wireless network operating under the control ofthe control station of the one such wireless network and being a newermodel than the control station of the one such wireless network, atleast one of said one such and said another such wireless networksproviding, in response to the control station of that wireless networkreceiving a request for constructing a new wireless network, atransmission time slot for said new wireless network.
 14. The wirelesscommunication system according to claim 13, wherein the at least one ofsaid one such and said another such wireless networks comprises: settingmeans for setting a time slot unassigned area to that wireless network;transmitting means for transmitting time slot assignment information ofthat wireless network; analyzing means for receiving and analyzing timeslot assignment information of another wireless network; and a assigningmeans for assigning a time slot of that wireless network using anunassigned area of a time slot in the another wireless network.
 15. Thewireless communication system according to claim 13, wherein saidconstruction request is a request for participation of another controlstation which constructs the new wireless network.
 16. The wirelesscommunication system according to claim 13, wherein said constructionrequest is a request from another control station, which constructs thenew wireless network, for a time slot to a control station of yetanother wireless network.
 17. The wireless communication systemaccording to claim 13, wherein information that a transmission time slothas been set to said new wireless network is included in time slotassignment information and notified in the new wireless network.
 18. Thewireless communication system according to claim 13, wherein atransmission frame for notifying said new wireless network of thesetting of a transmission time slot is transmitted to a control stationof said new wireless network.
 19. A non-transitory computer-readablemedium having recorded thereon a program for executing, on a computersystem, a wireless communication control method in a network environmentin which a plurality of wireless networks coexist in a same frequencyband, said method comprising: detecting a signal from another of saidwireless networks, each one of the wireless networks including anassociated portion of the plurality of wireless communicationapparatuses with one of the wireless communication apparatusesassociated with that wireless network operating as a control station forthat wireless network, the control station of each such wireless networkinitially performing time slot assignment within every predeterminedtransmission frame period to each one of said wireless communicationapparatuses of that wireless network independent of the control stationsof the other such networks; detecting address information of the controlstation of the another wireless network from the detected signal;comparing the address information of that control station with theaddress information of the control station of the another wirelessnetwork, and in response to the address information of that controlstation being newer than the address information of the control stationof the another wireless network, analyzing a transmission time slot onwhich guaranteed time slot transmission is performed in the another ofsaid wireless networks based on the signal detected in said signaldetecting step, and avoiding assigning a transmission time slot on whichguaranteed time slot transmission is performed on the another of saidwireless networks to a wireless communication apparatus in that wirelessnetwork.
 20. A non-transitory computer-readable medium having recordedthereon a program for executing, on a computer system, a wirelesscommunication control method in a network environment in which aplurality of wireless networks coexist in a same frequency band, saidmethod comprising: receiving, at a control station of one such wirelessnetwork, a request for constructing a new wireless network, each one ofthe wireless networks including an associated portion of the pluralityof wireless communication apparatuses with one of the wirelesscommunication apparatuses associated with that wireless networkoperating as a control station for that wireless network, the controlstation of each such wireless network performing time slot assignmentwithin every predetermined transmission frame period to each one of saidwireless communication apparatuses of that wireless network, the controlstation of the one such wireless network being a base station, thecontrol station of the new wireless network operating under the controlof the control station of the one such wireless network and being anewer model than the control station of the one such wireless network;at least one of said one such and said another such wireless networks,performing time slot assignment with a time slot unassigned area set inthat wireless network in response to said construction request, andtransmitting time slot assignment information in that wireless network.